# Tag Info

1 vote

### Advice for an AM detector using a BJT

Here is another trick for biasing a BJT near the cutoff current The current mirror here has been made out of Darlington pairs for increasing the input impedance. I have used the 2M2 collector ...
• 11

### Input filter vs damping resistor

The resistor reduces Q of the circuit, which helps reduce resonance (having a high gain peak), but worsens high-frequency attenuation (at high frequencies, L becomes an open circuit, R dominates, and ...
• 43.5k
1 vote

### Input filter vs damping resistor

When hit with an impulse, LC circuits will ring at a frequency determined by the inductance and surrounding capacitors. On a switching power supply input, there are current pulses where the edges act ...
• 10.5k
1 vote

### Input filter vs damping resistor

An inductor by itself will have a high Q. At some resonance frequency, the attenuation of the filter will be mostly defeated, and lead to a high EMC output or sensitivity. Shunting the inductor with a ...
• 171k
Accepted

### RC Filter Analysis

Circuit: simulate this circuit – Schematic created using CircuitLab KCL: \begin{align*} \frac{V_{_\text{OUT}}}{R_1}+C_1\frac{\text{d}}{\text{d}t}V_{_\text{OUT}}&=\frac{V_{_\text{IN}}}{R_1}...
• 11.8k

### Key fob frequency filter design

This is just a diode detector. The exact inductor value is unknown, even to the authors of that video. You will have to try until you see signal at the output. Is it a good circuit? No. Is the point ...
• 98.3k

### Key fob frequency filter design

1.35 pH is a too-small guess for inductance. Once again, a video has suggested, “hey, this is so easy”. To optimize this, coil inductance (likely in the hundred nanohenry ballpark) resonates with ...
• 27k

### What is the right way to model power converter noise? Should it be considered as voltage or current?

Current is correct for the most common cases: either the converter is a half-bridge (or two or three as an H or Ж bridge), including the non-synchronous buck case (one switch is passive i.e. diode), ...
• 43.5k
1 vote
Accepted

### LTspice issues with op-amp filter

You have two separate problems going on here. First, there is an issue with your Sallen-Key circuit that Carl Rutschow already pointed out in your question's comments. Restating, the inputs of your ...
• 4,896

### 7-section LC filter design

In filter design, you can scale inductor/capacitor ratio by choosing the termination resistance. In this design, perhaps the goal was fitting to standard-value 100uH inductors which had an adjusting ...
• 27k

### Converting short current pulses to TTL levels so they can be read with microcontroller

We want to invert the negative pulse, and amplify both to logic levels. The signal level is high enough that a modest amplifier can be used, single BJTs for example: simulate this circuit – ...
• 43.5k
Accepted

### Converting short current pulses to TTL levels so they can be read with microcontroller

The easiest way here seems to be choosing shunt resistor large enough to give you the required voltage for your MCU to register. To protect your MCU against overvoltage, a TVS diode to the supply ...
• 98.3k